CALIFORNIA
AGRICULTURAL EXTENSION SERVICE

CIRCULAR 104

September, 1937
Revised May, 1942

THE PRODUCTION OF

TOMATOES

IN CALIFORNIA

D. R. PORTER and JOHN H. MacGILLIVRAY

Cooperative Extension work in Agriculture and Home Economics, College of Agriculture,

University of California, and United States Department of Agriculture cooperating.

Distributed in furtherance of the Acts of Congress of May 8, and June 30, 1914.

B. H. Crocheron, Director, California Agricultural Extension Service.

THE COLLEGE OF AGRICULTURE

UNIVERSITY OF CALIFORNIA

BERKELEY, CALIFORNIA

CONTENTS

PAGE

Importance of the industry 3

Locations for tomato growing 6

Cropping systems 7

Fertilizers and manures 7

Growing the plants 8

Field culture 12

Irrigation 14

Staking and pruning 16

Unsatisfactory fruit setting 17

Harvesting, transportation, and yields 17

Varieties 19

Insects attacking tomatoes 30

Diseases of tomatoes 41

The tomato disease-control program 62

Acknowledgments 63

THE PRODUCTION OF TOMATOES IN
CALIFORNIA 1

D. R. PORTER 2 and JOHN H. MacGILLIVRAY 3

Profitable production of both market and canning tomatoes in Cali-
fornia involves many factors. Some of these may be controlled by the
grower; others, such as weather and market price, vary from year to
year. Profit depends on (1) yields, directly influenced by choice of varie-
ties, suitable soil, proper handling, and prevention of insect and disease
damage ; and (2) on time of maturity — in relation to market prices, this
being influenced by time of planting and by weather conditions during
the growing season. Indirectly these factors affect quality, which is then
reflected in the net returns to the growers.

Canning and shipping for fresh consumption are our two most im-
portant tomato industries. Our major problem, in canning, is the pro-
duction of solid-pack canned tomatoes (Extra Standard and Fancy
grades) ; and, in shipping, better transportation methods to prevent

losses in transit.

IMPORTANCE OF THE INDUSTRY 4

No state dominates in the production of tomatoes although California,
for some years, has been one of the leading tomato areas. From 1936 to
1940, on an average, 20.7 per cent of the total national crop was grown
in this state. California was first ; Indiana, which produced 14.8 per cent
of the total, was second. The five leading states — California, Indiana,
New Jersey, Maryland, and New York — produced about 60 per cent.
California led in 1940 with 24.0 per cent of the entire United States
tomato crop.

California tomato acreage has fluctuated markedly in the last few
years. During the five-year period 1936 to 1940 the acreage fluctuated
between 74,280 and 109,180. The 1940 value of sales of this crop was esti-
mated at $14,170,000.

Tomatoes for the Fresh Market. — California acreage for the fresh mar-
ket has increased slightly during the last five years. In 1940, about 17 per
cent of the total crop was shipped fresh — in the pink or green stage to

1 This circular supersedes Agricultural Extension Circular 66, Tomato Production
in California, by O. H. Pearson and D. R. Porter.

2 Associate Professor of Truck Crops and Associate Olericulturist in the Experi-
ment Station; resigned December 31, 1938.

3 Assistant Professor of Truck Crops and Associate Olericulturist in the Experi-
ment Station.

4 This section on certain economic aspects of tomato production was prepared by
John B. Schneider, Specialist in Agricultural Extension and Associate on the Gian-
nini Foundation.

[3]

California Agricultural Extension Service

[Cir. 104

distant points, and ripe to local markets. Although tomatoes are grown
in California every month of the year, the principal movement to out-of-
state markets comes in the fall (fig. 1). During 1940 California shipped
by freight a total of 3,850 cars, or about 17 per cent of the total United

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Fig. 1. — Monthly carlot shipments of fresh tomatoes from impor-
tant producing states in 1940. (Data from: United States Agricultural
Marketing Service. Carlot shipments of fruits and vegetables by
commodities, states, and months, p. 26. 1940 [Mimeo.].)

States carlot movement. About 35 per cent of California shipments were
made in October. The remainder of the movement to fresh market is of
about equal proportions ; but, being consumed in California and other
western states, the crop is moved largely by truck.

Tomatoes for Manufacture. — California acreage for manufacture, by
1937 had reached an all-time high of 83,030 acres. Estimates for 1941
indicated that 80,620 acres were planted. During 1940 about 83 per cent

The Production of Tomatoes in California 5

of the total production in California was used in manufacture. The
pack of tomato juice has been important for the last eight years ; that of
tomato paste has steadily increased until California has become the most
important producer. In 1940 the total pack of tomatoes in California was

Fig. 2. — California areas engaged in the production of tomatoes for
manufacture and shipping. (Data from table 1.)

13,419,448 cases. Of this total, juice accounted for 2,401,283 cases; paste
for 1,661,801. The remainder consisted of 5,244,003 cases of canned to-
matoes and 4,112,361 cases of miscellaneous products such as puree.

Tomato-producing Districts. — The distribution of commercial produc-
tion within the state is shown in figure 2. Shipping tomatoes are rela-
tively more important in southern California; canning in the north.
Table 1, showing the 1940 acreage by counties, indicates the location of
acreage planted to spring, summer, and fall-market tomatoes and also to
canning tomatoes.

California Agricultural Extension Service [Gib. 104

LOCATIONS FOR TOMATO GROWING

Before engaging in extensive production, the grower should be assured
of a profitable outlet; that is, he should have access to a good local mar-
ket, must be relatively near a cannery or other manufacturing plant, or

TABLE 1*

California Acreage of Tomatoes for Fresh Market and Canning
by Counties, 1940

County

Spring

Summer

Fall

Total for
market

Canni

Total all
tomatoes

Alameda

Butte

Contra Costa

Fresno

Imperial

Los Angeles

Kern

Madera

Merced

Monterey

Napa

Orange

Riverside

Sacramento

San Benito

San Bernardino .

San Diego

San Joaquin

San Luis Obispo

San Mateo

Santa Barbara. .

Santa Clara

Santa Cruz

Solano

Sonoma

Stanislaus

Sutter

Tulare

Ventura

Yolo

Total for state

4,000

100
100
300
200

4,000

2,500
100
300

1,750

1.400
700
100

700
300
150

100
300

1.000
900

11,000

700
2.000

1,100
300

100

1,000
100
300

700

900

1,500

500
350
850

100
50

1,200
200

11,950

100
2,300

200
4,000
3,600

400

300
1,750

100

2,400
800
400

1,400
1,200
1.650

500
450
150

100
50

1.000

2,100

200

26,950

11,306

100

3,577

4,029

463

329

848

1.039

194

8,726

3,748

1,640

561

17,697

1,042

5,284

1,518

877

329

143

1,015

6,931

71,531

12,106

200

5,877

200

4,000

7,629

400

300

2,213

429

848

3.439

994

9,126

3,748

1,640

1,961

18,897

1.740

1,542

5,734

1,150

1,518

110

927

329

1,143

3,115

7,131

98,481

* Source of data:

Schiller, Carl M. Vegetable crops in California. California Cooperative Crop Reporting Service,
Sacramento, March, 1941. (Mimeo.)

must be so situated that he can ship to advantage. Usually he should not
plan on shipping unless the available acreage is large enough to make
carload lots possible, either for himself or for groups or associations of
small growers located in the same community. He should carefully con-
sider the season at which the crop will mature and the market conditions
probable at that time.

The Production of Tomatoes in California 7

The tomato, a heat-loving plant, is favored by the long growing season
in most parts of the state. Localities subject to late-spring or early-fall
frosts or having a very cool summer climate are usually not suitable.

Although the tomato succeeds on many soils, soil type and fertility
may influence yield, quality, and time of maturity. Sandy soils promote
early maturing, whereas heavier soils seem to favor late-maturing or
fall crops. Good drainage is essential. The tomato plant will root deeply
unless prevented by plow sole, hardpan, or poor drainage. The history
of the land from the standpoint of alkali content is also important, for
the tomato is very susceptible to alkali injury.

CROPPING SYSTEMS

Since tomatoes are a cash crop, they are frequently grown for several
successive years on the same field. Rotation experiments have shown that
continuous growing of tomatoes will result in a reduction in yield and
frequently an increase in soil-borne diseases. Observation would indi-
cate that tomatoes give good yields after alfalfa or sugar beets harvested
early the previous fall. Other crops which are not closely related to
the tomato botanically may also be used to advantage in the rotation.
The tomato crop in northern and central California is sometimes rotated
with a winter crop of spinach. After picking is finished in November the
tomato plants are pulled and burned so that the land may be fitted and
sown to spinach at once. The spinach crop is harvested in March and
April; and the land is prepared for tomatoes again, the plants being
transferred to the field in May. This combination, though good, may
lead to loss if the same land is continuously cropped. In general, tomatoes
should be grown only once in four years on the same piece of land —
obviously in rotation with other crops. Certain diseases and insects often
become prevalent when tomatoes are grown continuously. Double-crop-
ping of land with winter vegetables and tomatoes is practicable only
when the tomato crop can be irrigated.

Some growers wrongly suppose that tomatoes have an injurious effect
upon subsequent crops. Dead tomato vines and green fruits, plowed
under, are actually beneficial from the standpoint of the added organic
matter. When they are piled and burned, however, the accumulation of
ash may injure the next crop.

FERTILIZERS AND MANURES

Tomatoes apparently respond to nitrogenous fertilizers on some of
the light, sandy, or gravelly soils in the southern part of the state. On
neutral or alkaline soils ammonium sulfate is desirable because it does
not increase the alkalinity of the soil. A maximum application of this

8 California Agricultural Extension Service [Cir. 104

material is usually 300 to 350 pounds per acre. The plant needs much
more fertilizer late in the season than when first set out. Unsatisfactory
growth may result from hardpan, alkali, disease, poor drainage, or faulty
irrigation.

The fertilizer should be applied in bands 4 to 6 inches on each side of
the plant at a depth of 6 inches or more. If fertilizer is applied in an open
furrow before plant setting, it should be thoroughly mixed with the
soil to prevent injury to the roots. Some of the plant setters have at-
tachments for applying the fertilizer in continuous bands on both sides
of the plants.

Fertilizer tests have been conducted by farm advisors, individual
growers, and canners. In some districts certain fertilizers have resulted
in increased plant vigor and yield. In Riverside County ammonium
sulfate (250 pounds per acre) has proved satisfactory and economical.
San Diego County growers are convinced of the value of fish meal, am-
monium sulfate, or ammonium phosphate. Trials near Davis with either
treble superphosphate or complete fertilizers have shown no change in
yield. Tests made in Contra Costa County near Brentwood on "green
wraps" for several years have shown a response in yields from the appli-
cation of ammonium sulfate. At Santa Maria complete fertilizers tended
to produce a higher yield than ammonia alone. Winter covercrops have
increased succeeding tomato yields in Los Angeles County.

GROWING THE PLANTS

The method to be used in growing the plants will depend upon the
length of growing season and the value of early tomatoes. Part or all
of the crop may be sold on the fresh market or grown for sale to canning
factories. Since earliness is often a prime factor in fresh tomatoes, more
expense is justified in producing them. In the northern and central parts
of the state the plants are started in a hotbed or cold frame and are
removed to the field in the spring after the danger of frost is past. As
soil temperature affects the percentage and rate of germination, a day
temperature of at least 65° F should be maintained until the seedlings
appear, and then not allowed to go lower than 55°. The best method of
growing plants will depend upon the locality and season at which the
crop is desired. Certain diseases originating in the plant bed are dis-
cussed in a later section.

The Hotbed and Cold-Frame Method. — The use of hotbed and cold
frame is generally best for early market crops and is also used even for
the late shipping and canning crops in central and northern California.

The hotbed frame should be located in a warm, sunny, well-drained
spot. Though the best covering is glazed sash, unbleached muslin (grade

The Production of Tomatoes in California 9

DD) is also satisfactory, especially if waterproofed. Any heat necessary
for the hotbed may be supplied from fresh horse manure, steam, hot
water, or electric soil cable. In a manure hotbed, 4 to 8 inches of fresh
horse manure is placed in the bed and tramped down, and a layer of soil
4 inches deep is placed over this. In many localities the use of electricity
is practicable and permits adequate control of the soil temperature. A
sandy soil or a mixture of half sand and half garden soil is best for the
hotbed : it gives stronger plants with better root system than very fertile
or heavy soil. The seed is usually planted 8 to 10 weeks before the field

Fig. 3. — The type of cold frames used for plants growing in cen-
tral and northern California. They are 8 to 12 feet wide; the sides
and ends consist of 1 by 12 inch boards; and the frames are covered
with sheets of unbleached muslin. The seedling plants from the
hotbeds should be transplanted into these cold frames about 2 by 4
or 2 by 6 inches apart. (From Ext. Cir. 6Q.)

transplanting season. It is broadcast at the rate of 1 ounce per 10 to 15
square feet of hotbed space. The seedlings are transplanted to a cold
frame 2 inches apart in the row and with rows 3 to 4 inches apart. The
hotbed should be kept warm and moist until the plants are up. Thereafter
it should be well ventilated during warm days and watered sparingly.
Before tomato seedlings push through the ground it has been the prac-
tice in one area to kill all the weeds with a blow torch.

As soon as the seedlings show their first rough leaves they are ready
to be transplanted to another bed, usually a cold frame (fig. 3). This
task is worth doing carefully. The cold frames, though usually wider
than the hotbeds, are prepared much the same except that no artificial
means of heating is used. About 4 inches of fine soil, preferably a mix-
ture of one part garden soil, one part sand, and one part rotted manure,
all well mixed and passed through a screen of ^-inch mesh, should be
placed in the cold frame. A suitable covering for the frames may be

10 California Agricultural Extension Service t GlK - 104

made of unbleached muslin sewed together in sheets or tacked to frames
of convenient size for handling ; burlap sacking is sometimes used. The
covering should slope sufficiently to shed all rain and thus prevent the
wetting of plants and surface soil.

The seedling plants from the hotbed are usually set in the bed about
2 by 4 inches apart. Water should follow transplanting ; and the frames
should be kept covered a few days until the plants have taken root,
especially if the sunlight is strong or the weather windy. Once reestab-
lished, the plants should be given only enough water to keep them grow-
ing moderately. All watering should be done in the late morning so that
the soil surface and the foliage will be dry by evening. It is important
that during the daytime the frames be ventilated in order to obtain short
plants with thick, stocky stems and to reduce the damage by damping-off
organisms.

A variation in the hotbed method described above is to transplant the
seedlings into small clay pots or into "dirt bands" from which they can
be removed without disturbing the roots. This method, though more ex-
pensive, may be profitable to the market gardener who caters to a de-
mand for extra-early fruit on a local market. Often, too, gardeners and
seedsmen transplant the seedlings to boxes (flats) about 18 by 24 inches
in size and 3 inches deep.

From 3 to 6 days before the plants are transferred to the field the beds
should be left open continually unless frost threatens, and only enough
water applied to prevent prolonged wilting. This treatment toughens
or hardens the plants so that they may be removed without severe wilt-
ing, which so often kills tender plants in the open field. Well-hardened
plants resist frost somewhat better than succulent ones, and they take
root more rapidly.

The Cold-Frame Method. — Tomato plants may be started in cold
frames in localities where they must be sown during cool weather but
not so early as to require the hotbed method. Frames are prepared in a
sheltered, sunny spot ; and a 4-inch layer of sandy, moderately fertile
soil is then placed in them. The seed is sown by hand or with a seed drill,
being planted thinly in rows 4 to 6 inches apart. After germination the
beds should be weeded, and the plants thinned to about one for every two
inches. This method produces a large number cheaply; but it seldom
results in good, large, stocky plants with well-developed roots, because
the seed is usually planted too thickly and the necessary thinning is not
done. The plants are pulled and transplanted directly to the field from
the cold frame.

The Open-Bed Method. — The open bed, probably the cheapest way to
grow plants, is not adapted to sections with short growing seasons nor

The Production of Tomatoes in California

to early crop production. It is used for the late shipping crop in south-
ern and coastal districts and may also be suitable for late market crops
elsewhere when relatively quick-maturing varieties are used. In this
method beds are prepared in a well-drained, sheltered spot, preferably
sandy. Narrow beds, 30 to 36 inches from center to center, are thrown
up with a lister ; the ridges are harrowed down and leveled. Two rows
are sown on each bed, and the furrows between the beds are used for
irrigation. The seed is drilled in with a seeder as soon as the soil becomes

■

; ;

i/"

Fig. 4. — Type of protection from cold given tomato plants in the Coachella
Valley: brush and paper are used as cover, with the south side left open. These
plants are not to be staked.

warm and frost danger is over. With favorable temperature for germi-
nation, 20 seeds may be planted per foot, and thinned to 12 per foot.

Care of Plant Beds. — Regardless of the bed type the soil must be
weeded and cultivated to prevent crust formation. Thinning is often
necessary, for crowded plants are susceptible to the damping-off dis-
ease and develop weak, spindling stems. Particular care should be given
to watering the plant beds; overwatering produces weak, sappy, "leggy"
plants that recover slowly after being transferred to the field. Excessive
moisture, especially late in the day, favors damping-off, a disease that
sometimes destroys many plants overnight. Waterings should usually
come several days apart and not till wilting has begun, since no harm
is done if the plants are checked temporarily by lack of water. Holding
plants for a long period of time after they have reached transplanting
size is undesirable. One should therefore not plant earlier than is neces-
sary to get the correct size at the desired time.

12 California Agricultural Extension Service [Gib. 104

The day before the transplanting, the beds should be watered so that
the plants can be removed easily. The soil should be loosened with a
spade or similar tool to minimize root injury caused when the plants
are pulled from the bed.

Seeding in Place in the Field. — In sections with a long growing season
tomatoes may be planted directly in the field. This method is wasteful
of seed, involves considerable labor in thinning, and cannot be practiced
when tomatoes follow a winter crop of spinach or other vegetables. On
the other hand it lessens the expense, the interruption of plant growth,
and the danger of damping-off that occurs under the transplanting
process. Since early infection of mosaic usually comes from the use of
tobacco by people who are transplanting, this direct seeding method
eliminates this cause of reduced yield. The seed is set in hills before frost
danger is over and is thinned later to one plant per hill. Various types
of plant protectors are used.

In the Imperial Valley almost the entire acreage is ordinarily grown
from plantings made directly in the field and protected with brush and
paper shelters (fig. 4) until danger of frost is past.

FIELD CULTURE

Tomato land had best be deeply plowed in the fall ; after spinach or
other winter crops the ground should be plowed as soon as possible after
the winter crop is removed. In the spring, before the soil surface be-
comes hard and dry, the land should be disked and floated to kill the
weeds and to pulverize the surface soil. The method of preparing for
the plants and of transplanting depends upon the locality and the soil
conditions. In some sections, when planting for the early crop, one may
set the plants without watering if the soil is handled properly. Under
such conditions the field is leveled and marked off in both directions.
The plants, if set by hand, are then placed at the intersections. In set-
ting large acreages one may use a mechanical transplanter (fig. 5) . These
machines set the plants as well as they are usually set by hand; and water
may be applied in the same operation.

In dry sections, and in most sections during dry seasons, the plants
must be watered as they are transplanted. This is almost always the case
in setting the late crop. If irrigation is practicable the simplest plan is
to cross-mark, then to plow out a furrow for each row. The plants are
set at each cross-mark on the edge of the furrow, and a small stream of
water is turned into each row as it is set. Cultivation must follow within
a day or two to prevent a hard crust from forming around the roots. At
this time one should work the soil toward the plants, and thus begin the
bed, which should be formed gradually for each row.

The Production of Tomatoes in California

Transplanting reduces growth, and this growth reduction is propor-
tional to root injury. The plants are set 3 or 4 inches deeper than in the
plant bed and are placed carefully so that the roots are not "doubled

■ . ■ ■■

Fig. 5. — Upper: Planting tomatoes by hand near Centerville. A
large portion of the tomatoes grown are planted in this way, almost
as cheaply as by machine. One man can plant about 1*4 acres per
day, but there is no overhead for machine depreciation in this method.
Lower : Planting tomatoes by machine near Hollister. Two machines
are drawn by one tractor ; two men on each machine place and water
the plants; one man follows on foot to be sure that every plant is
properly aligned ; and one man drives the water truck to supply the
tanks on the machines. (From Ext. Cir. 66.)

back." New roots develop along the old stem, giving a more extensive
root system than can be obtained when the plant is set shallow. Deep
setting, though more laborious, enables the plants to use the moisture in
the lower soil.

14 California Agricultural Extension Service [Cm. 104

Planting Distances. — The planting distance is determined by the
variety, the soil, the season at which ripe fruit is desired, and whether
or not the plants are to be staked. Early tomatoes under intensive cul-
ture where the plants are staked and trained to a single stem, as in the
Merced district, are set 15 inches by 3 feet apart, so that 12,000 plants
are required per acre. The late shipping and canning crop of such vari-
eties as Norton, which generally make vigorous vine growth, are set 6
by 6 feet; and the Santa Clara Canner at the same distances or 6 by 8
feet. The late varieties, then, require from 1,000 to 1,200 plants per acre.
Further modification may be necessitated by moisture and fertility con-
ditions. A wider spacing is necessary under dry farming than under
irrigation.

Although wide spacings are more economical of plants and labor than
the close plantings, the ideal spacing will vary with different climatic
and soil areas and so no definite rule can be given. Certainly the rows
must be wide enough to allow cultivation, irrigation, and dusting or
spraying, and to permit easy passage for the pickers without injury to
the plants. Experiments in which two plants are set in a hill show slightly
less total yield from the two than from a single plant.

IRRIGATION 5

Tomato crops can be grown satisfactorily in some parts of the state
with little or no irrigation — for example in the districts with over 15
inches of winter rainfall and a cool summer, like the San Francisco Bay
region. In some of these districts, however, increased yields may be se-
cured by irrigation ; and in many other sections growers depend on this
practice for maximum yields. The number and frequency of applications
are determined by local conditions — chiefly by the type of soil, the tem-
perature during the growing season, and the plant growth habit. Suffi-
cient water should be used to keep the plant growing steadily without
wilting. The principles of irrigation and soil moisture seem to be the
same for tomatoes as for many other plants. These principles are dis-
cussed in detail in a previous publication. 6 For adequate irrigation of
tomato plants all the dry soil should be wetted. This purpose is best
accomplished by using several small furrows between the rows and by
wetting as much of the soil as possible ; if it is necessary to irrigate while
the plants are small one ditch close to the row of plants may be used
(fig. 6) . As the plants increase in size it may not be practicable to main-
tain several furrows between the rows because of the injury to the plants.

5 This discussion of tomato irrigation was prepared by L. D. Doneen, Assistant
Irrigation Agronomist in the Experiment Station.

6 Veihmeyer, F. J., and A. H. Hendrickson. Essentials of irrigation and cultiva-
tion of orchards. California Agr. Ext. Cir. 50:1-24. Revised 1936. (Out of print.)

The Production of Tomatoes in California

Fig. 6. — Tomatoes furrowed for the first irrigation after transplanting.
Fruit-setting on these plants has already begun. (From Cir. 263.)

Fig 7. — Irrigation of tomatoes from slip-joint pipe. By use of a V-crowder
a basin 2 feet wide has been made between the rows. This arrangement is
advisable where the land slopes very steeply. Since the lateral movement of
moisture is negligible, however, a furrow closer to the plants would be more
effective. After a run of 6 hours the moisture had not penetrated more than
6 inches to each side of this basin. (From Cir. 263.)

Instead, a broad low ditch may be formed for irrigation (fig. 7). Since
the lateral penetration of water is slow, this ditch should be maintained
as wide as the size of the plants will permit. Keeping the surface soil dry
under the plants during the latter part of the season will minimize the
loss caused by fruit rots.

16 California Agricultural Extension Service [ Cir - 104

According to experimental results, the only benefit derived from
cultivation is through weed control. Weed cutting or scraping of the
surface is all that is needed once the plants have become established.

Tomato plants, being deeply rooted, draw water from a large volume
of the soil. If the soil is filled with water, as after a winter rainfall or a
heavy irrigation, the plants may go uninjured without additional water
for several months. As recent investigation has shown, growth is unin-
terrupted until the lack of moisture causes wilting or a curling of the
leaves; in some varieties this may be indicated by a slight change in
color. According to these results, if the supply of soil moisture becomes
dangerously low, it is possible to irrigate the soil and replenish the soil
moisture before the plant is injured or growth retarded. Where the rate
of evaporation is high, as in the interior valleys or in the Imperial Valley,
water is applied approximately three times during the season with 5 or
6 inches per irrigation for the heavy soils. Lighter soils are irrigated

more frequently.

STAKING AND PRUNING

The tomato plant naturally forms an erect stem, with spreading side
branches developing from the axil of each leaf. Under the special form
of culture known as staking and pruning, the side shoots are removed
as they appear. They should be pulled out of the axils of the leaves, for
pinching with the finger nail is apt to spread virus diseases. The growth
is thus limited to the main or central stem, which is kept erect by being
tied at intervals to stakes or to wires stretched between stakes. On such
plants the crop is limited to the fruit borne in the clusters that form
at every third or sixth node on the central stem. If a strain of Earliana
is grown one may better protect the fruit from sunburn and somewhat
increase the yield by leaving two main stems per plant instead of one.
Staking obviously reduces the number of fruits per plant, but this draw-
back is partly offset by the closer spacing. Plants to be staked and pruned
may be spaced 15 to 18 inches in the row, and the rows 3 feet apart. This
arrangement gives three or more times as many plants per acre as with
an early variety grown without staking and pruning. Judging from ex-
periments, staking and pruning result in a greater production of early
fruit per acre. On the other hand the procedure involves higher costs of
production per acre for labor, plants, and materials. At Merced, yields
of about 6-10 tons of salad tomatoes per acre and 6 tons of canning
tomatoes have been secured. Fall yields on staked tomatoes have been
recorded as high as 40 tons per acre. Labor in caring for the plants,
pruning, tying, and staking amounts to about 85 man-hours per acre.
The Pritchard variety is used at Merced because of its determinate type
of growth which reduces pruning costs. Although much of the early crop

The Production of Tomatoes in California 17

for shipping raised near Merced and other cities in northern California
is grown in this way, the staking and pruning methods of culture should
be limited to home gardens and to early market crops or when the area
available is very limited.

UNSATISFACTORY FRUIT SETTING

The development of a tomato fruit begins when the active portion of
the pollen unites with the active portion of the ovule. This phenomenon,
known as sexual fertilization, is followed by active and rapid growth of
the fruit. Many factors may affect these processes and consequently the
set of fruit and the yield.

Insufficient nutrients or an abundance of nitrogenous fertilizer may
cause rapid elongation of the style and prevent normal pollination.
Insects may eat or destroy certain essential parts of the flowers. As more
recent research has demonstrated, average temperatures as low as 50°
F and as high as 100° tend to prevent fruit setting and temperatures of
70° to 85° are more favorable.

HARVESTING, TRANSPORTATION, AND YIELDS

The exact stage of maturity at which the fruit is picked depends upon
the purpose for which it is intended. For local markets, for canning, and
for pulp manufacture the fruit when picked should be fully colored but
firm. Nothing is gained by leaving it on the plant after it is fully colored.
For shipment to nearby points it is harvested "pink," when about half
the surface shows distinct color. For shipment to distant markets it is
usually picked "green-mature" — fully grown but not yet showing pink
or red. Such fruit, however, should appear yellowish at the blossom end.
A green-mature fruit, cut open, is found to have the cells (locules) well
filled with the gelatinous pulp in which the seed is embedded.

In preparation for shipment, tomatoes in all these stages of ripeness
are picked once a week or oftener. The ripe fruit, however, is placed in
separate containers by the picker and is sold on the local market or to
the canner. The pink fruits that are just turning and the green fruits
are hauled together to the packing shed to be sorted, graded, wrapped,
and packed for shipment.

Breaking or bruising the fruit skin or flesh during handling should
be avoided. The stem should be removed as the fruit is picked in order
that it may not puncture the skins of other fruit when packed.

Packing. 7 — The two containers most used in California are the four-
basket flats and the Los Angeles or Mexican lug. The latter type is used

7 Storing, ripening, and packing of tomatoes are fully discussed in : Parsons, F.
Earl. Preparation of fresh tomatoes for market. U. S. Dept. Agr. Farmers' Bui.
1291:1-32. 1922. Eevised 1937.

18 California Agricultural Extension Service [ Cir - 104

mainly for eastern shipment. Canning tomatoes are handled in 50-pound
lug boxes supplied to the growers by the canners at a nominal rental.

Artificial Ripening. — Fruit packed green-mature ripens and colors up
within one to three weeks, according to the storage temperature and the
degree of maturity when picked. Upon reaching market the shipment
is unwrapped, fruit showing sufficient color is sold at once, and fruit
still green or only partly colored is placed in special ripening rooms. In
gathering green-mature tomatoes careless pickers take many that are
not mature. The latter are worse than a total loss, for they never attain
good edible quality when artificially ripened and tend to depress prices
even for high-quality tomatoes. Tomatoes picked in the "turning" stage,
when they show a little pink at the blossom end, are more uniformly of
high quality when artificially ripened than those picked green.

Temperatures between 60° and 70° F are recommended for ripening
but not for storage. Below 60° the ripening process is very slow. The
maximum storage life of tomatoes is obtained with a temperature at 55?
They can be held for not more than three weeks at this temperature and
on removal to a temperature of 70° will attain ripeness in another week.
If stored at less than 50° for more than a few days, the fruit does not
develop good color or flavor when removed to higher temperatures. Pro-
longed cold storage of either green or ripe tomatoes is therefore im-
practicable.

Ripening in storage can be accelerated by adding small amounts of
ethylene gas to the air. A concentration of 1 part ethylene to 2,000 to
4,000 parts of air has proved effective. It will reduce by 4 to 7 days the
time required to change tomatoes from green to full red. The gas is
obtained in compressed form in steel cylinders, from which the proper
amount is discharged into the ripening room each day. The room must
be approximately airtight to prevent too rapid loss of the gas. As oxygen
is also essential for normal ripening, fresh air should be admitted each
day. Favorable temperatures must be maintained in the ripening room
even when ethylene is used. Though explosive in mixtures of 1 to 3 with
air the gas is not dangerous in the above low concentrations.

Yields. — The yield depends upon variety, cultural practices, length
of harvesting season, and damage by insects and diseases. Tomatoes pro-
duced for a spring shipping crop yield only about 3 tons of salable toma-
toes to the acre, as in the Imperial Valley. For fall shipment a yield of
4 to 6 tons per acre or even more is not unusual unless the season is short-
ened by frost.

Canning tomatoes, however, are much more productive. From 7 to 12
tons is the usual yield, and under favorable conditions 15 to 30 tons have
been reported.

The Production of Tomatoes in California 19

Problems of the Tomato Grower and Canner. — California as a canning
state has the advantages of high yields, better-than-average color, "low
mold count" on the fruits, and an opportunity in periods of good prices
to can tomatoes after frost has killed eastern plants. Our western toma-
toes are low in active acidity and have a greater percentage of sugar
so our processing times are considerably longer than in the east. This
results in breaking down of the canned tomatoes which is frequently
referred to as the solid-pack problem. Buyers of canned tomatoes want
the fruits to come out of the can in a whole condition and where they lack
this characteristic they are sold as Standards at a lower price. There
have been many years when less than 10 per cent of our canned tomatoes
have been solid-pack or quality canned tomatoes. The quality demands
of canned-food brokers and wholesalers greatly influence the prices re-
ceived for canned tomatoes and prices paid the growers.

VARIETIES

Because tomatoes are grown under diverse soil and climatic conditions
in California, many varieties are used. The crop from Imperial Valley
is intended mainly for green-wrap shipment. In other districts the crop
is used for distant shipment, local market, and varied canning and pre-
serving purposes. In some localities the hazard from f usarium wilt neces-
sitates the planting of resistant varieties.

Many varieties have been developed whose fruits, though early matur-
ing, are unsuited for shipping and usually too small for canning. Toma-
toes of certain other varieties are too large or too rough for fresh-fruit
markets but are used for manufacturing.

Profitable production in certain districts is threatened by such diseases
as spotted wilt and bacterial canker. One logical remedy is to develop
resistant varieties. New varieties for greenhouse and field are constantly
being developed throughout the world. As time and facilities permit,
these new varieties are tested under varying environmental and soil con-
ditions in California. Tomato growers should be prepared to accept new
varieties that have proved satisfactory and to cooperate with the Agri-
cultural Experiment Station in testing such varieties when they are
released.

The following discussion covers the varieties now most extensively
grown in California.

Earliana. — Although several improved strains of Earliana are now
available, the two most generally used are First Early and Morse's 498.
The original Earliana was flat and rather rough, but the improved
strains just mentioned usually produce smooth, globular fruit (fig. 8).
The plants are comparatively small and weak- growing, and require only

20 California Agricultural Extension Service [ Cir - K* 4

Fig. 8. — Characteristic fruit of the Earliana variety.
This tomato typically is a slightly lobed and flattened
sphere, smooth at both stem and blossom ends. The blos-
som end often has a medium-sized scar; light-colored
lines radiating from this scar are a striking characteris-
tic of the variety. The walls of the fruit are thin, and
the core is not pronounced. Fruits shown natural size.
(From Ext. Cir. 66.)

The Production of Tomatoes in California 21

one third as much space per plant as late varieties. The fruit is red, early
maturing, but small compared with late varieties. Earliana is excellent
for the extra-early crop where growers cater to a local market. It is
extensively used for spring shipments from Imperial Valley.

Mar globe. — Marglobe was introduced in 1925 by the late F. J. Pritch-
ard of the United States Department of Agriculture. It is the result of
hybridizing the Marvel and Globe varieties, followed by selection for
the fusarium-wilt-resisting quality of Marvel and the shipping quality
of Globe. These characters have been combined in Marglobe to a satis-
factory degree. In addition this variety possesses considerable resistance
to nailhead spot (Alternaria) , a serious disease in some sections outside
California. Largely for this reason, Marglobe is being used extensively
in the southern states and in Mexico. It is planted in the San Joaquin
Valley, in the coastal section from San Luis Obispo south to San Diego,
and in the interior districts of Los Angeles, Riverside, Orange, and San
Bernardino counties. In short, Marglobe is the most important tomato
variety in California, as well as in the United States, for both canning
and shipping. The fruit is round, red, medium-sized, good in shipping
quality, and medium early in maturity (fig. 9) .

Norton. — In the interior districts of southern California and in Santa
Barbara and Ventura counties the Norton variety is being used both as
a shipping and canning variety. It is also resistant to f usarium wilt and
has almost entirely replaced Stone, from which it was selected, in these
districts. The fruit is red, slightly flattened (fig. 10), usually smooth,
free from "cat faces," medium to large in size, and late maturing.

Early Santa Clara. — This variety, though not extensively used for
fresh-market purposes, is important for canning in the coastal districts
from Salinas north and in the interior valleys north from Fresno County.
It resulted from selections out of Santa Clara which in turn had been
obtained from the Trophy variety. The latter was for many years an
important variety in the Santa Clara Valley. Similar strains are known
as San Jose Canner and Cal. 55. The latter is a selection out of San Jose
Canner. It is slightly later-maturing than Early Santa Clara, but the
fruit is smoother.

The plants grow extremely vigorously and bear until frost stops
growth. Despite its rough fruit, this variety is extensively used in the
districts mentioned above: it apparently possesses some tolerance to
verticillium wilt in the coastal districts, usually produces a high yield,
and is a popular canning type because it is thought to give higher yields
than other varieties. The fruits are very large, much flattened, red, usu-
ally deeply corrugated at the stem end (fig. 11), and often marred by a
large irregular scar at the blossom end.

California Agricultural Extension Service t ClR - 104

Fig. 9. — Typical fruit of the Marglobe variety. The
side and cross walls are especially heavy. The fruit is
either spherical and slightly flattened, or blocky like a
cube with rounded edges. It has a tendency toward wide,
corky, longitudinal cracks at the stem end, although the
skin is tough. Fruits shown natural size. (From Ext.
Cir. 66.)

The Production of Tomatoes in California

Fig. 10. — Typical fruit of the Norton variety. This tomato is
slightly roughened at the stem end, often with a pronounced scar at
the blossom end. It is flat, usually somewhat oval in cross section. The
interior is very often "seedy," and the walls are not especially heavy.
The core tends to be rather prominent. The fruits of Stone and
Greater Baltimore are very similar to Norton in appearance. Fruits
shown natural size. (From Ext. Cir. 66.)

California Agricultural Extension Service [Cir. 104

Fig. 11. — Fruits of the Early Santa Clara Canner variety. The upper picture
shows the natural size and the lobed stem end. Below are reduced vertical and
cross sections of twenty fruits showing the range in size and internal structure.
The fruit of this variety, though variable, is typically heavy-walled, with many
small seed cells in the interior of the central fleshy mass. This is the tomato most
extensively used for canning and manufacture in central and northern Cali-
fornia. (From Ext. Cir. 66.)

The Production of Tomatoes in California 25

The Variety, 133-6. — This variety, developed by the Ferry-Morse Seed
Company, was selected out of Cal. 55, mentioned above. It resembles
Marglobe in type (fig. 12) , being much smoother than Early Santa Clara
but more "meaty" than Marglobe. It is also slightly tolerant of verticil-
lium wilt. It is used in the coastal sections and the Los Angeles area for
shipping and canning.

Pearson. — This new variety was created by Dr. 0. H. Pearson, for-
merly of the California Agricultural Experiment Station. Released in

Fig. 12. — Fruits of the variety known as 133-6, selected by plant breeders
of the Ferry-Morse Seed Company from the original Cal. 55, which was devel-
oped by the late Dr. J. T. Eosa of the California Agricultural Experiment Sta-
tion. This variety is used for both shipping and manufacture. It is not adapted
to culture in the hot interior districts. (Courtesy of the Ferry-Morse Seed
Company.)

1933 as Hybrid No. 65, it has proved valuable enough to merit a name.
It resulted from a cross between Cal. 55 and Fargo, an early-maturing
variety developed by Dr. A. F. Yeager at the North Dakota Agricultural
Experiment Station.

The plant habit differs from that of standard varieties in being deter-
minate ( "self -pruning" or "self-topping"). Most varieties of tomatoes
might be regarded as perennial — that is, capable of continuing their
growth (if not killed) more or less indefinitely ; and normally they pro-
duce a blossom cluster at every third leaf (fig. 13). Such varieties, obvi-
ously, bear fruit over a long period. The so-called "determinate" growth
habit is manifested by relatively few varieties : such plants often produce
blossom clusters with only one leaf between, and eventually the stem
terminates in a blossom cluster (fig. 14) ; the energy of the plant is then
chiefly used by the fruit, for blooming has ceased. Determinate plants,

California Agricultural Extension Service

[Cm. 104

then, usually require less space in the field than plants of the standard
type, such as Marglobe and Santa Clara. Furthermore, if insecticides
or fungicides must be applied, determinate vines, which cease elongat-
ing, are less liable to be injured by the wheels of spray or dust machinery
than standard vines.

Fig. 13. — Branch of a standard or indeterminate tomato vine. The growing
tip remains vegetative, and there are usually three leaves between blossom clus-
ters. (Courtesy of Dr. A. F. Yeager, North Dakota Agricultural Experiment
Station.)

The fruit of Pearson is a slightly flattened globe, intermediate between
Marglobe and Norton (fig. 15) . It is deep red, smooth, with a tough skin,
heavy walls, and numerous cells, and averages slightly larger than Mar-
globe and seldom cracks. Its tough skin, firmness, smoothness, size, shape,
and color make it valuable for green-wrap shipment. It yields well and
recent selections by seed companies have been used successfully by can-
ners for their different products. The acreage of these new selections is
increasing.

For maximum development, however, this new variety appears to
require abundant plant food and moisture. The vine is relatively small
and bushy and is inclined to set an exceptionally heavy crop (fig. 16) ;
thus it needs adequate food and water to produce desirable fruit size

The Production of Tomatoes in California

and abundant foliage as a protection against sunburn injury. This
variety has been grown with success in the Lower San Joaquin Valley,
in the delta of the Sacramento and San Joaquin rivers, around Sacra-
mento and in the Los Angeles area in Southern California.

Fig. 14. — Branch of a determinate tomato vine. Note that the branch termi-
nates in a flower cluster, and elongation therefore ceases. Determinate plants
are thus more compact and less sprawling than standard vines. (Courtesy of Dr.
A. F. Yeager, North Dakota Agricultural Experiment Station.)

San Marzano. — This variety (fig. 17), which is called an Italian Pear
type, was first used in the state about 1926. It has steadily grown in popu-
larity until 20,000 to 25,000 acres are now being grown. It is especially
popular with the paste canners near Stockton and Modesto.

It is used primarily by paste packers for blending with the "round"
varieties because of its better color and increased consistency of the fin-
ished product. In recent years it has been used for solid-pack tomatoes
with a rapidly increasing production. This variety is less acid than most
varieties canned in California. The variety has a tough skin, is two-
celled, but will remain on the vine for a long period, so picking may be

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The Production of Tomatoes in California

Fig. 15. — Typical fruits of the Pearson variety, characterized as slightly
flattened globes. This tomato is well adapted to coastal conditions and to Los
Angeles and Riverside counties. Some of the newer selections are finding favor
with the canners of northern California. (Courtesy of the Haven Seed Company.)

Fig. 16. — A single plant of the Pearson, a high-yielding, smooth-fruited variety,
determinate in habit of growth. (Courtesy of the Haven Seed Company.)

California Agricultural Extension Service

[Cm. 104

less frequent. The last picking is usually performed by cutting the vines
at the surface of the soil and a few days later shaking the tomatoes off on
the ground. The fruits may be picked up more rapidly from the ground
than off the vine.

Other -Varieties. — Many additional varieties have been and are being
used. A variety known locally as Bush Stone is widespread in San Joa-
quin County. Pritchard is grown locally in southern California and for
stake tomatoes in the Merced area. The vine is similar to Pearson. Car-

Fig. 17. — San Marzano, the most important variety of the Italian Pear type,
showing a cluster of nine fruits. (Courtesy of the Haven Seed Company.)

nera, which is similar to 133-6, is one of the important canning and ship-
ping varieties of Southern California. The characteristics of the seven
most important tomato varieties grown in California are listed in table 2.

INSECTS ATTACKING TOMATOES 8

Two types of tomato insect damage occur in California. Direct damage
is caused by insects feeding on roots, foliage, or fruit ; indirect by certain
insects spreading disease. The role played by the latter is discussed in
connection with diseases.

The control of many tomato insects in California has been investigated
and considerable information has been obtained concerning the effective-
ness of varioiis insecticides and proper time of application under north-
ern California conditions. In many places where the hornworm or the
corn earworm is destructive, insecticides apparently must be applied
while the fruit is ripening. Where tomatoes are grown for the cannery
there is no serious objection to such applications, since the cannery wash-

b The section on insects was prepared by Dr. A. E. Miehelbacher, Junior Entomolo-
gist in the Experiment Station.

The Production of Tomatoes in California

ers can be equipped to remove the poisonous residue. For fresh market
more care is essential. If dusted when mature, the fruit may need wash-
ing or careful wiping. At present arsenicals and fluosilicates provide
best control for the hornworm and the corn earworm. Although consid-
erable work has been done with light traps, further study is needed.

Only standard brands of arsenicals and fluosilicates should be used
for controlling tomato pests, and of these only preparations having the
smallest amount of water-soluble toxic elements should be selected. Lead

2gi«K*.

Fig. 18. — Stages in the life cycle of the corn earworm: A, mature
larvae; B, pupa removed from earthen cell; C, pupa within earthen
cell; D, adult in a position of rest; E, adult with wings spread. All
shown natural size. (From Bui. 644.)

arsenate has proved very effective against the corn earworm and the
hornworm, but as it contains two toxic elements, calcium arsenate or
cryolite should be substituted.

With insecticides there is always some slight danger of direct injury
to the tomato plants. The grower should therefore select the material
known to be the safest for his district. In the past no material used in
experimental work caused any serious burning.

Masks should be furnished workers applying dusts of any kind.

Corn Earworm, Heliothis armigera. — The adults have a wing spread
of about 1% inches and are fawn-colored, with darker spots on the fore-
wings and with a brown margin and a transverse brown band on each

32 California Agricultural Extension Service [ Cie - 104

hind wing (fig. 18, D and E). The moths may live 2 weeks or longer,
during which time one female may deposit 500 to 3,000 eggs. The eggs are
round, somewhat flattened, white or pale yellow, and longitudinally
ribbed with fine lines. In warm weather they hatch in 3 or 4 days.

Under favorable conditions the larvae may mature in 2 or 3 weeks.
When full grown they are about 1% inches in length (fig. 18, A). They
show a great variation of color, ranging from pale green to almost black
and may be marked with stripes of pink, yellow, brown, or other colors.
On completing their development they burrow into the soil and construct

Fig. 19. — Corn-earworm damage to tomatoes : A, advanced injury of the stem
end, with caterpillar in burrow; B, tomato cut in half to show the internal de-
struction caused by the caterpillar. (From Ext. Cir. 99.)

pupal cases a few inches below the surface. The pupae (fig. 18, B and C)
vary from dark amber to chestnut brown and are about % inch long.
The pupal period lasts 2 to 3 weeks during the summer. Many of the
larvae that pupate by the middle of September, or even before, are
apparently overwintering forms. In California there are at least three
generations a year.

The corn earworm is one of the most serious pests attacking the tomato
fruit, although sweet corn is probably the preferred host. In central
California the pest probably builds up on other host plants before
migrating extensively into the tomato fields. The eggs are laid at random
over the periphery of the vines. After hatching, the larvae begin feeding
and often burrow into the fruit, usually at the stem end. Where an
infestation is heavy, 25 per cent or more of the fruit may be destroyed.
The type of injury produced is illustrated in figure 19.

Every year there are probably some sections where the injury is not
sufficient to justify control measures.

Control. — The importance of proper applications of insecticidal dusts

The Production of Tomatoes in California 33

for corn-earworm control cannot be overemphasized. Thorough distri-
bution with proper equipment will insure efficient control, savings in
materials, and the elimination of complicating dust residues. If the vines
are completely covered with not more than 15 to 25 pounds of calcium

.HP* ! - ' : "'^9

wr ^V

I m

Fig. 20. — Tomatoes seriously infested with the to-
mato pinworm, showing the several types of injury.
(From Bui. 625.)

arsenate per acre, preferably when dew is on the plants, a high degree
of control may be expected. It is not necessary to concentrate materials
on the fruits — this, in fact, is an undesirable practice.

Cryolite dusts have also been found to be effective. Best results have
been obtained where cryolites from natural sources have been used. The
cryolite content of a dust should be not less than 50 per cent and it may
be desirable to use it at a strength of 60 to 70 per cent. On large vines
the dust should be applied at the rate of 30 pounds per acre, although
smaller amounts may suffice where dusts containing the larger amounts
of active ingredients are used.

34 California Agricultural Extension Service t ClR - 104

Calcium arsenate is as easily applied as any of the effective materials,
and has proved better than cryolite in the control of hornworms. Horn-
worms are among the most destructive insects attacking tomatoes over
a large portion of the northern tomato-producing section. Growers in
this region can obtain satisfactory control of both corn earworms and
hornworms with calcium arsenate dust properly applied.

Tomato Pinworm, Gnorimo schema lycopersicella. — The pinworm is
one of the most destructive tomato pests in California. Although it has
caused most serious losses in the southern districts, it is rather widely
spread throughout the state and some damage has occurred in the north-
ern producing sections. The adults are small gray moths % inch in
length. The small larvae are pale with dark heads ; the older larvae, green
with purplish markings. The mature larvae are about % inch long and
at a glance appear grayish or greenish purple. Though principally a
pest of the fruit (fig. 20), the pinworm also attacks the vines. The larvae
generally enter at the stem end of the fruit, where they are often unno-
ticed until picking time. Even then a careful inspection is necessary to
detect the injury, particularly if the larvae are small. Feeding is con-
fined to the core and the fleshy portions radiating from it. At the time
of picking, the entrance to the burrows may be open ; but after the fruit
is allowed to stand, the larvae web them over. The injury resembles that
caused by the larva of the potato tuber moth.

Control. — Control of this pest has been worked out by entomologists
of the United States Department of Agriculture stationed at Alhambra ;
they have found cryolite to be the most effective insecticide. It is applied
as a dust and the cryolite content should not be less than 50 per cent.

Because the tomato pinworm builds up in large numbers in abandoned
fields, all plants should be destroyed immediately after harvest, either
by plowing or by burning the refuse. Piles of infested plants should
never be allowed to remain in the field or elsewhere.

Potato Tuber Moth, Gnorimoschema operculella (Phthorimaea) . —
This moth is widespread in many districts of California. There are sev-
eral generations a year. The adults, which fly by night, are gray, with
small silvery bodies, and have minute dark specks on the f orewings. The
female lays 150 to 200 eggs, small, oval, pearly white, and deposited
indiscriminately over the plant. When fully grown the larvae are slightly
over % inch in length and are white, yellow, pinkish, or greenish, with
the head and prothoracic shield dark brown. The tuber-moth larvae can
be distinguished from pinworm larvae by their lighter color and larger
size. They are pests of the fruit (fig. 21) and cause damage similar to
that done by the pinworm.

Control. — Although some injury may occur in many fields, serious

The Production of Tomatoes in California 35

damage is usually observed only where tomatoes followed potatoes or
were being grown in areas largely devoted to potato culture. To avoid
severe attack, therefore, it is probably best not to follow potatoes with
tomatoes. Serious infestations are almost certain to occur if volunteer
potato plants are not destroyed.

Cutworms and Armyworms. — These worms can be divided into two
groups. The first group contains those worms which feed at night and

Fig. 21. — Tomato infested at the calyx end by the larva of the potato tuber
moth. The calyx has been removed, revealing the excrement and the entrances
to the burrows. (From Ext. Cir. 99.)

hide in the soil or in the debris covering it during the day. In the second
group are placed those armyworms that spend their entire larval period
on the plant. Members of the first group are controlled with poison baits.
The following bait has proved satisfactory :

Bran 50 pounds

Molasses 2 quarts

Sodium fluosilicate 2 pounds

Water sufficient to make a nearly dry mash.

If sodium fluosilicate is not obtainable, paris green, arsenic trioxide,
or calcium arsenate can be substituted. The dry ingredients should be
thoroughly mixed and the molasses dissolved in water before being
added. The mixture should be stirred with just enough water added to

California Agricultural Extension Service

[Cir. 104

moisten the mash. Too much water will cause the mash to be sticky, and
difficulty will be encountered in spreading it.

Because most armyworms feed at night, the best time to scatter the
bait is at dusk. This allows a maximum time for the caterpillars to feed,
for once a bait drys out, it is no longer very attractive to the pest. If a
field is known to be infested, the bait should be broadcast over the field
a day or two before planting. If the plants are already set out and are
being injured by cutworms, a small amount of poison bran should be
scattered around each plant.

Fig. 22. — Tomato injured by the yellow-striped armyworm,
Prodenia praefica. (From Bui. 625.)

The yellow-striped armyworm, Prodenia praefica, and the sugar beet
armyworm, Laphygma exigua, belong in the second group. The yellow-
striped armyworm may do serious damage to tomato. Not only does it
feed on the foliage but it may also seriously attack the fruit (fig. 22).
Unlike the corn earworm, it does not enter the fruit, but eats large irregu-
lar holes in its surface.

The sugar beet armyworm is primarily a foliage feeder, although it
frequently injures the fruit, but, since it is characteristically an external
feeder, fruit injury is usually superficial. Damage from its attacks is
usually most serious where fruit is grown for the green market.

Both the yellow-striped armyworm and the sugar beet armyworm can
easily be controlled by thoroughly dusting the vines with undiluted com-
mercial calcium arsenate at a rate of from 10 to 25 pounds to the acre,
the amount to use depending upon the size of the vines.

Hornworms, Protoparce sexta and P. quinquemaculata. — Both of
these hornworms are very destructive over part of the tomato-growing

The Production of Tomatoes in California

section of California ; the greatest damage is done in the warmer interior
valleys. The adults, which fly by night, are known as sphinx or humming-
bird moths and are strong, swift fliers. They are gray, with yellow spots
on the sides of the body; their wing expanse is 4 to 5 inches (fig. 23, B).
There are no less than two generations a year, and activity may begin

Fig. 23. — The tomato hornworm: A, larva; B, adult.
(From Ext. Cir. 87.)

early in June and continue until frost. The spherical, smooth, pale-green
eggs are laid at random over the plants. After hatching, the larvae grow
rapidly, sometimes attaining the length of 4 inches. They are predomi-
nantly green, with a characteristic spine or horn at the posterior end
(fig. 23, A) . The larvae are chiefly pests of the vine, although when abun-
dant they may destroy both blossoms and fruit. Where no control is prac-
ticed they may strip the vines. At maturity they burrow into the soil,

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[Cir. 104

where they construct an earthen cell and transform into chestnut-brown
pupae (fig. 24) about 2 inches long. They pass the winter in the pupal
stage in the fields.

Control. — When the hornworms first appear in the field and the vines
are still small, hand-picking and destruction are practical. Later, where
an infestation is severe, the field may need dusting several times a season.

Fig. 24. — A, Pupa of the tobacco hornworm; B, pupa
of the tomato hornworm in its cell. The distinguishing char-
acteristic separating the two species is the sheathed pro-
boscis, which is longer in the tomato worm. (From Ext.
Cir. 99.)

Arsenicals seem more effective than cryolite. Straight commercial cal-
cium arsenate dusted evenly and thoroughly over the plants at the rate
of 15 to 25 pounds per acre should prove effective.

Flea Beetles. — These minute insects jump quickly; they eat small
holes in the leaves, and are a pest chiefly during the early stages of plant
growth. Injury can be reduced with any of the following dusts : pow-
dered lead arsenate, 1 part to 4 parts of dry lime ; or a 70 per cent barium
fluosilicate ; or a cryolite dust, 40 per cent.

Darkling Ground Beetles. — The beetles, Blapstinus sp. and Metopo-
nium abnorme, are small — scarcely more than % inch long — and dull
black or bluish black. They live in the soil and are destructive chiefly
because they girdle plants. They can be controlled by using the following
bran mash, scattered over the ground at planting time.

The Production of Tomatoes in California 39

Bran (or dried, ground beet pulp) 25 pounds

Arsenic trioxide, calcium arsenate, or paris green 1 pound

Molasses 2 quarts

Mix the arsenic trioxide dry with the bran, and add the molasses after
diluting somewhat with water. Stir thoroughly : add enough water to
make a dry mash that will broadcast easily. The molasses may be omitted
without greatly lessening the effectiveness of the bait. Calcium arsenate
or a 40 per cent barium fluosilicate dust is also effective. Some growers
have obtained excellent control by heavily dusting the plants with lime
when they are first set out.

Vegetable Weevil. — Considerable injury may sometimes be caused by
the vegetable weevil, Listroderes costirostris (L. obliquus). For control
on young plants a 70 to 80 per cent cryolite dust may be applied with a
knapsack or bellows duster at the rate of 10 to 12 pounds per acre; a
puff or two to each plant, enough to cover thoroughly the foliage and the
ground at the base of the plant, gives protection.

Tomato Mite, Phyllocoptes destructor. — Little is known as yet con-
cerning the habits or seasonal cycle of this mite which has recently
proved to be a serious pest. It is a free-living, microscopic mite which
crawls about slowly on the surface of the stems and leaves. Under high
magnification it is whitish yellow in color and slightly humped. It has
legs only on the forward portion of the body. Like similar mites, such
as the silver mite of peaches and the pear bud mite, it sucks out the cell
contents of the surface of the stems and leaves, producing a brown or
russeted appearance.

The injury first begins to appear in June and does not become serious
enough to be noted until late July and August. Starting at stalks near
the ground, the infestation works up the plant, gradually causing the
lower leaves to dry up. During hot weather a rapid defoliation of the
plants sets in, resulting in sunburned fruit. Only in very serious cases,
and after the leaves are all killed, does the mite affect the fruit itself.
Up to the present time it has been most serious in the warmer interior
valleys.

Control. — Dusting sulfur gives the best control of all materials tested
to date. Even under temperatures as high as 108° F no burning of the
vines has been apparent. However, some canning concerns have a restric-
tion on the use of sulfur on canning tomatoes. Others will allow growers
to use a 25 per cent sulfur dust. When this is allowed a mixture of dust-
ing sulfur and calcium arsenate dust can be used. Such a dust, if applied
at 25 to 30 pounds to the acre, should materially reduce mite damage
and also control hornworms, the corn earworm, and other army worms.
The area of severest mite damage also covers the region where early dust-

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[Cir. 104

ing for hornworms may be necessary. If the mixed dust is used for the
control of hornworms in July and August it is probable that a serious
mite infestation will not develop. Extensive experimental work with
a mixture of dusting sulfur and calcium arsenate dust is being con-

Fig. 25. — Boots of tomato plant affected by nematodes — the root-knot disease.

(From Cir. 280.)

ducted, and, if it proves successful as expected, the cost of pest control
in heavily infested mite regions will be materially reduced. On market
tomatoes there is no restriction and sulfur dusting will keep the mite in
check for 3 to 4 weeks.

Nematodes, or Eelworms, Heterodera marioni. 9 — The garden nema-

9 Tyler, Jocelyn. The root-knot nematode. California Agr. Exp. Sta. Cir. 330:1-38.
Eeprinted, 1937.

The Production of Tomatoes in California 41

tode or eelworm is not an insect but a true roundworm of microscopic
size. This pest, a general feeder, causes a common disease known as root
knot, which attacks many plants (fig. 25). On the fibrous feeding roots
of tomato it produces gall-like swellings that weaken and eventually kill
the plant. The first indication of this pest is the stunted, yellowed appear-
ance of the plants in the field.

Control. — No satisfactory method has been developed for controlling
this pest once it has become established in the soil. Since nematodes are
frequently distributed on seed potatoes or on rooted vegetable plants,
every precaution should be exercised to avoid bringing them from in-
fested soils into the field and seedbeds. Kotation, using resistant crops
on infested soil for two or three years, has proved helpful in starving
out nematodes. Iron, Monetta, and Victor cowpeas, velvet beans, cereals,
grasses, peanuts, soybeans, and onions are reportedly resistant.

Caution. — Since many insecticides are poisonous to man and animals,

they should be used cautiously. This is particularly true of poison bait,

for there is danger that chickens or children may eat it, perhaps with

serious consequences. Cattle or other animals should be kept away from

freshly dusted fields. Poisonous insecticides should not be applied to

plants after the fruit begins to color if the crop is being produced for

market. If dusted after the fruit is mature, the fruit should be carefully

wiped or washed.

DISEASES OF TOMATOES 10

Tomatoes in California are subject to many diseases, any one of which
may cause considerable loss. Curly top, for example, a virus disease
spread by the sugar-beet leaf hopper, has significantly curtailed produc-
tion in the southern San Joaquin Valley, although it is not a serious
hazard in the Sacramento Valley or along the central coast. Likewise
late blight, a wet-weather disease, occurs only in the southern coastal
counties but may cause heavy loss if early fall rains occur. Bacterial
canker, a serious seed-borne disease, is much less localized, whereas the
less destructive mosaic is statewide. In certain localities, mostly coastal,
the thrips-transmitted spotted wilt disease is a limiting factor. In the
interior valleys fusarium wilt causes loss unless resistant varieties are
used.

Damping-off . — Damping-off, which occurs primarily in the seed and
plant bed, is caused by one or a combination of several soil-inhabiting
fungi, among them Pythium, Bhizoctonia, Sclerotinia, and Fusarium.
The organisms involved enter the stem of young seedlings at the soil
surface and cause a rapid disintegration of the stem tissue. The first

10 This discussion of diseases was prepared by C. E. Scott, Extension Specialist in
Plant Pathology.

42 California Agricultural Extension Service C Cm - 104

symptom is a slight drooping at the tips of the young leaves and a gen-
eral lack of turgidity of the plants. A marked wilting soon develops, and
then the stem shows a water-soaked condition at the surface of the soil.
Diseased plants soon fall to the ground, bending at the soil line, and,
if high humidity prevails, the weblike threads of the fungus grow over
the fallen plants. Damping-off is usually first evident in small areas in
the bed. Unless checked, however, it spreads rapidly, destroying large
areas or, in some cases, the entire bed.

Damping-off is favored by humid conditions and by a lack of adequate
ventilation. Plant beds should be located on well-drained soil covered
with about % inch of nematode-free sand. This arrangement allows the
surface to dry more quickly and makes conditions less favorable to the
disease. After the seedlings emerge the beds should be sparingly watered
and well ventilated. When climatic conditions permit, the beds should
be opened by midmorning, watered, and left open until well into the
afternoon. The beds should not be watered before being covered again in
the afternoon, even though the surface soil appears dry. The surface
should be kept as dry as possible whenever the plants are covered.

Since the organisms that cause damping-off are commonly found in
the soil, one method of control is soil disinfection by chemicals or steam.
Heat treatments are effective against both nematodes and damping-off
fungi. Formaldehyde applied either in a liquid form or as a formalde-
hyde-dust mixture is effective against the fungi but not against nema-
todes. Carbon disulfide and chloropicrin are effective against nematodes
and fungi under some conditions. All eradicant soil treatments are ex-
pensive and more or less difficult to apply.

Damping-off of tomatoes can usually be controlled to a satisfactory
degree by two simple practices. Dry seed should be treated with yellow
copper oxide at the rate of one teaspoonful per pound of seed. After
emergence the seedlings should be sprayed at 7- to 10-day intervals with
yellow copper oxide, 1% pounds per 100 gallons. The same spray may
also be used on the soil surface immediately after planting.

Fusarium Wilt. — This wilt, caused by the soil fungus Fusarium
lycopersici, is a serious disease in certain regions where high soil tem-
peratures prevail. It causes some loss, for example, in the early staked
crop of the San Joaquin Valley and in the camiing crop of the Delta,
the Sacramento Valley, and the warm valleys near the coast, but in gen-
eral it is not serious in strictly coastal areas.

The leaves of infected plants turn yellow, usually first on one side of
the plant; later the plant dies prematurely. A light-brown discoloration
is evident in the woody cylinder of the stem, but there is no disintegra-
tion of the pith or open cracking as with bacterial canker. The yellowing

The Production of Tomatoes in California 43

of one branch often caused by Rhizopus canker, where an early-ripened
and rotted fruit is attached, should not be confused with fusarium wilt.
The disease may attack plants at any age, whereas verticillium wilt pri-
marily affects older bearing plants.

The fusarium attacks only tomatoes and persists in the soil from year
to year, entering the plant through the roots. It is favored by soil tem-
peratures of 80° F and above and is most severe on the lighter, well-
aerated, well-drained types of soil that heat up promptly. It may be
introduced into fields by infected transplants and may also be seedborne.

A number of wilt-resistant varieties have been developed, among them
Marglobe, Norton, Pritchard, and Rutgers. These may be used on in-
fested soils. The adaptability of these and other varieties is discussed
in another section.

Verticillium Wilt. — The wilt, caused by the soil fungus Verticillium
alhoatrum, occurs under cooler soil conditions than fusarium wilt and
therefore is more common along the coast. It usually affects older plants,
causing the older leaves to wilt and die prematurely. Affected plants
show a brown discoloration in the woody cylinder when the stem is cut
near the crown of the plant.

The fungus persists in the soil from year to year and infects numerous
hosts, such as strawberries, cotton, eggplants, and stone fruits. Certain
strains of the Santa Clara Canner variety show appreciable tolerance of
the disease.

Late Blight. — Late blight, caused by Phytophthora infestans, some-
times causes losses in the late fall crop in San Diego, Orange, Los An-
geles, Ventura, and Santa Barbara counties after early fall rains, mainly
as a result of fruit infection. Infection also occurs in the plant beds in
the spring.

The disease is characterized by rapidly enlarging brown or black
blotches on the leaves (fig. 26), petioles, and stems, which cause a rapid
blighting of the tops, and by greenish-brown areas on the green fruit,
lobed at the margin and slightly sunken, with a somewhat corrugated
surface that is firm and hard to the touch (fig. 27). These lesions first
appear as small, water-soaked, greenish-brown blotches but enlarge very
rapidly until half or more of the fruit surface is involved. Sometimes
three or four lesions may occur on the same fruit. It is difficult to detect
incipient infection when the green fruit is packed ; the lesions develop
rapidly in transit and during storage in the ripening rooms. This fungus
usually invades only the outer-wall regions, producing a shallow, dry rot,
but secondary rot-producing organisms often invade the fruit through
the blight lesions. The lesions frequently start at the stem end, but may
originate at other points also.

California Agricultural Extension Service [ Cir - 104

Fig. 26. — Symptoms of late-blight infection on tomato leaf. The
blotches are at first water-soaked ; later they become greenish brown
or black. A white mold forms on the undersurface, from which the
disease spreads to other foliage.

Under very moist conditions a whitish velvety outgrowth of the fungus
occurs on the leaf and stem lesions. This moldy growth is formed by
the sporophores and spores of the fungus ; the spores, spread by wind,
induce disease in healthy plants when wet.

Since the fungus may persist in old overwintered tomato plants and
may be carried thence to seedlings or young plants in the plant bed, all
overwintered tomato plants in the neighborhood of the plant beds should
be destroyed.

The Production of Tomatoes in California

Late blight may be prevented by spraying or dusting with a copper-
containing fungicide. Whether spraying or dusting is practiced will
depend largely upon the equipment available, the weather, and the topog-
raphy of the land. If a wet spray is used, a 4-4-50 bordeaux mixture is
recommended. Bordeaux mixture is prepared by dissolving copper sul-

Fig. 27. — Symptoms of late blight on tomato fruit. Small, greenish-brown
blotches enlarge and later become dark brown. The interior tissues become water-
soaked and soon decay. Often a white mold develops on the surface.

fate (Milestone) in water to make a stock solution containing 1 pound
of copper sulfate per gallon. A separate stock solution of lime is prepared
by slaking processed or stone lime, or by soaking fresh hydrated lime
and then diluting with water to make a stock solution containing 1 pound
of lime per gallon.

The spray mixture is prepared by filling the spray tank two thirds full
of water and then adding enough copper sulfate stock solution to make
a solution containing 4 pounds of copper sulfate for each 50-gallon
capacity of the spray tank. With the agitator running an equal amount

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[Cir. 104

of the lime, stock solution is then added and the tank filled with water.
For example, with a 100-gallon spray tank 8 gallons of each stock solu-
tion would be required to make 100 gallons of 4-4-50 bordeaux mixture.
Special spraying machines adapted for treating two or three rows at
a time are used ; they should have three nozzles for each row. Tomatoes
should be sprayed at a pressure of 100 or more pounds per square inch
to make certain that all parts of the plant are reached. Several applica-
tions are necessary to protect new growth from infection : the first should

-■.

Fig. 28. — Early-blight leaf infection. This disease occurs in plant beds in

wet seasons.

be made at the earliest evidence of disease in the field, and the treatment
should continue at intervals, according to the air temperature and hu-
midity. The amount of spray solution required for each application will
vary from 100 to 300 gallons per acre, according to the size of the plants
and the width of the rows.

If a dust mixture can be more conveniently applied, copper-lime dust
is recommended. This fungicide may be bought already prepared, or it
can be made at home by mixing together 15 pounds of monohydrous
copper sulfate and 85 pounds of hydrated lime. The ingredients are best
mixed in a revolving wooden barrel. The dusting schedule is the same
as for spraying.

Early Blight. — The fungus Alternaria solani is the cause of early
blight which occurs sometimes in the plant beds in early spring after
prolonged wet weather and occasionally on the maturing crop along the
coast. This disease is characterized by small, dark-brown, irregularly

The Production of Tomatoes in California

Fig. 29. — Early-blight lesions on green tomato fruits.

ijlj

■;,::IS

■ : 1 »

Fig. 30. — Collar rot resulting from plant-bed stem lesions of the early-blight
fungus, Alternaria solani. The stem eventually breaks as the plant is whipped
about by the wind.

California Agricultural Extension Service

[Cm. 104

circular lesions on the leaves (fig. 28), each of which when closely exam-
ined shows concentric lines. Black cankers also appear on the stems of
young plants, and small irregularly circular spots or large brown stem-
end lesions on the green fruits late in the season (figs. 29 and 30) .

Plants from infected beds should not be used particularly if there is
any stem infection. When plants with stem lesions are set out in the field,
these lesions continue to enlarge and finally girdle and weaken the stem,

Fig. 31. — Pleospora rot. This stem-end rot causes some
loss in late-fall shipments to the east from the Salinas
Valley.

and produce collar rot (fig. 30) . As the plant grows larger and is whipped
about by the wind, the stem may break at the point where it is weakened
by collar rot. Infected plants may be dwarfed and what few fruits are
formed may ripen prematurely. Plant beds should be moved to a new
location if early blight has previously caused trouble. Spraying in the
plant beds with yellow copper oxide, will check this disease. (See direc-
tions under control of damping-off for spray schedule.)

Pleospora Rot. — The rot caused by Pleospora lycopersici (Macrospo-
rium sp.) affects the stem end of the ripening fruit (fig. 31) in certain
coastal areas and has caused considerable loss in November and De-
cember shipments to eastern markets. Infection takes place through
cracks and wounds near the stem end of the fruit, where a firm, dark-

The Production of Tomatoes in California 49

brown spot develops. Progress of the rot is checked at 45° F and is most
rapid between 65° and 70? Other fungi may also infect growth cracks
and cause a rot of the ripe fruits.

Leaf Mold. — The leaf mold caused by Cladosporium fulvum usually
occurs only on greenhouse tomatoes. It produces large yellow patches
on the upper leaf surface and a brown velvety growth on the lower side.

Fig. 32. — Effect of bacterial canker on seedlings. The wilting leaves on the
plant to the right are the first symptoms. The plant to the left shows a later
stage with cankers on the stem.

Infected leaves die prematurely. Thorough sanitation and disinfection
of the greenhouse before plants are set out, lowering the relative humid-
ity by adequate ventilation and heating, and irrigating properly will
minimize leaf -mold losses. Leaf mold occasionally occurs on staked toma-
toes in the field near the coast.

Bacterial Canker. — This disease caused by the organism Aplanobac-
ter michiganense blights the lower leaves, which become lighter brown
than those dying from other causes. Plants infected when young produce
very few salable fruits. Yellowish streaks may be produced on the stems,

California Agricultural Extension Service

[Cir. 104

which eventually crack open, forming cankers (fig. 32). The interior of
diseased stems is brown and mealy, especially at the nodes; the pith may
be easily separated from the woody portion. The infection also extends
into the leaf stems, and, when the leaf is cut off, a yellowish ooze may be
squeezed from the cut end of the petiole.

The canker bacteria pass through the stem into the fruit and some-
times into the seed. Fruits infected when very young are stunted and
distorted, but those infected late show no external symptoms.

Fig. 33. — Symptoms of bacterial canker on a young plant found in the field.
Note the cankers on the stems and the dead leaves on the side branches. This
plant probably became infected in the plant bed when it was cut back. (Note
the stem stub at left.) Plant pruning is apt to spread various diseases.

Infected plants may be found in the plant bed. They may be detected
by wilting and dying of the lower leaves and sometimes by a yellowish
streak or crack along the stem.

Infection is carried with the seed and apparently spreads consider-
ably in the plant beds. The disease is introduced into the field with the
transplants. There is little or no natural spread of infection in the field
under California conditions. Cutting off the tops of the plants (fig. 33)
either in the bed or in the field may spread the disease. The disease is also
spread by handling during planting as is evidenced by its occasional
marked prevalence in certain rows. Field carryover seldom occurs in
California (fig. 34).

The Production of Tomatoes in California

The bacteria are carried both within and on the seed. Experiments in
Utah and California show that seedling infection may be prevented if
the seed is fermented when separated and later disinfected.

The available information indicates that the following precautions
help to minimize losses from canker :

1. Purchase canker-free seed.

2. Select seed from fields free from the disease.

3. Ferment the pulp or the entire crushed tomato, without adding
water, for 3 to 6 days at or below 68° P. Stir the fermenting pulp twice
a day.

Fig. 34. — A field showing tomato plants severely injured by bacterial canker in
the Sacramento Valley in 1935. Since almonds had occupied this land for many
years, the soil was free of the canker organism. Infection took place in the plant
bed, very probably from diseased seed or soil.

4. Disinfect the dry seed any time before planting by immersing in a
solution of bichloride of mercury (corrosive sublimate) to 1 to 3,000 for
exactly 5 minutes and then washing immediately in running water for
15 minutes. The treating and washing may be done by placing the
seed in a loose muslin bag before immersion and agitating the bag
constantly to insure rapid wetting of all the seed. After removing the
bag from the treating solution, the open end can be tied around a water
faucet and the water turned on with sufficient force to insure rapid
washing of the seed.

5. Locate plant beds in soil not previously used for tomatoes. Disinfect
old plant-bed lumber with formaldehyde (1 pint to 5 gallons) or copper
sulfate (1 pound to 10 gallons) .

6. Plants should not be used from beds showing even a trace of canker.
With purchased plants, make reasonably certain that the grower took
precautions to exclude this disease.

7. Do not top the plants.

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[Cm. 104

Bacterial Speck. — A black spotting of the leaves (fig. 35) may occur
in field plant beds where overhead irrigation is used. The spots are greasy
and lack the concentric lines that are present in lesions of early blight.
Bacterial speck is not serious and disappears upon transplanting to the
field. The organism causing the disease is Bacterium punctulans.

Spotted Wilt. — This disease is caused by a virus transmitted by flower
and onion thrips and causes tremendous damage in the coastal districts.
It infects many ornamentals, weeds, and truck crops, besides being very
destructive to tomatoes.

Fig. 35. — Bacterial speck on leaflets of young plants in field
plant bed.

In vigorously growing tomato plants this disease causes a sudden
blighting and death of the growing tips (fig. 36). Plants affected at this
stage make little further growth and bear no crop. Careful examination
shows that the blighting was preceded by numerous circular dead spots
on the young leaflets or by a bronzing (fig. 37) of the upper surfaces of
these leaflets, and by the appearance of dead spots or streaks on the
petioles and stem. Occasionally such plants are killed outright ; but usu-
ally they remain alive, subsequent shoot growth being greatly dwarfed
and rosetted, with the leaflets showing severe malformation of the
mosaic type.

Infection of young plants in the plant bed is evidenced by numerous
small circular dead spots on the young leaves and by prompt death.
Visibly infected plants, therefore, seldom survive transplanting.

When older bearing plants are infected the blighting of the growing
points is accompanied by some yellowing of the leaves and conspicuous

The Production of Tomatoes in California

Fig. 36. — The leaflet at the left shows the circular brown spots characteristic
of early stages of spotted wilt. Streaking of stem and petiole, darkening of the
pith, and leaf blighting caused by spotted wilt are shown at the right.

circular patterns in the pigment of the immature fruits, often in the
shape of light-green concentric circles (fig. 38). On ripening fruit, circu-
lar yellow spots appear on a red background, or red spots on a yellow
background — an effect especially objectionable in the crop grown for
late-season shipment to eastern markets.

California Agricultural Extension Service [C 1r - 104

When plants are infected with both the mosaic virus and the spotted
wilt virus, a common condition late in the season, the spotted-wilt symp-
toms are more severe, but the characteristic circular shape of the spots
and patterns on leaves and fruits is often lacking. Extensive and irreg-
ular areas of dead tissue occur on and in the fruits. The term streak has
been applied to this combination of virus diseases as well as to spotted
wilt alone.

Fig. 37. — Spotted wilt on leaflets of tomato plants showing yellow-
ing, bronzing, and apical burning of leaflets.

The spotted-wilt virus is transmitted by the flower thrips and the
onion thrips. The larvae of the thrips pick up the virus, and remain
infective well into the adult or winged stage. Symptoms appear in the
plant 2 or 3 weeks after infection occurs. The virus may be transmitted
by rubbing leaves of a healthy plant with juice from a diseased one; but
such infection seldom occurs under field conditions.

Over a hundred species of plants have been found infected by the
spotted-wilt virus, including such crops as celery, lettuce, pepper, and
horse bean ; and such ornamentals as calla, aster, nasturtium, tuberous
begonia, gloxinia, cineraria, calceolaria, delphinium, dahlia, petunia,
zinnia ; and such weeds as nettle, chickweed, Jimson weed, wild lettuce,
and mallow. Of course infected plants of any species are potential sources
of infection for tomatoes.

The disease is serious in tomatoes only in the coastal regions, perhaps
because there is no freezing weather to reduce the reservoir of infection
in winter crops, ornamentals, and weeds; or perhaps because the flower

The Production of Tomatoes in California

thrips abound in those districts. The disease has proved serious in the
interior valleys only when introduced on transplants grown near the
coast or where there are nearby market gardens growing truck crops

Fig. 38. — Spotted wilt on tomato fruits. Circular and concentric chlorotic
patterns on green fruits (upper) and yellow spots on a red background on a
mature fruit (lower).

year-round. Late season infection may occur to a limited degree in the
Delta region and the Sacramento Valley, probably as a result of infec-
tive thrips being blown in from the Bay region.

In parts of the coastal districts spotted wilt is so prevalent that toma-
toes cannot be profitably grown, whereas in general the attack is scat-
tered and may take a toll of 10 to 25 per cent of the crop by early infec-
tion, with considerable increase later in the season.

56 California Agricultural Extension Service [ Cir - 104

Frequently spotted wilt occurs in the plant beds, and crops set from
such beds are heavily infected. Being usually located near the residence,
and therefore often near ornamentals and dooryard gardens, such beds
are readily reached by infective thrips.

No effective control has been found. The difficulty of controlling thrips
is well known. Spraying with nicotine in the field or plant bed has not
been effective. Certain precautions, however, are recommended : Plant
beds for tomatoes should be located as far as possible from home gardens
or flower beds and from alfalfa, which harbors the flower thrips abun-
dantly during the winter. All weeds should be kept out of the plant beds
and off the surrounding land. Old plant beds that are to be used again
should be kept clean-cultivated all summer. It is best not to use plants
from beds in which infection is present; certainly no plants should be
purchased from such beds.

Plants which become infected when young will bear no fruit and con-
sequently should be rogued out as long as it is not too late to replace
them with healthy plants.

In the greenhouse crop, spotted wilt may be controlled by fumigating
once a week or of tener to kill thrips and by removing all sources of infec-
tion, such as weeds, ornamentals, and diseased tomato plants.

Curly Top. — This disease, also called western yellow blight, is caused
by the same virus that produces curly top in sugar beets and is the most
serious tomato disease in the San Joaquin Valley ; occasionally it is prev-
alent in certain coastal valleys and south of the Tehachapi Range. Early
tomatoes grown in the San Joaquin Valley suffer some loss from curly
top, and heavy infection occurs in certain seasons in the northern San
Joaquin Valley, particularly near the foothills. Infected plants, though
not usually killed, are a total loss so far as marketable fruit is concerned.

Tomato curly top is spread by the beet leafhopper, Euttetix tenellus.
In years of extensive outbreaks its severity varies with the number of
hoppers that invade the cultivated regions from different parts of a
natural breeding area. The direction of the wind at the time of the hopper
flights is believed to control the amount of infection in the migratory
regions of the insect. Since the beet leafhopper breeds on sugar beets,
tomatoes grown near this crop usually suffer greater loss than those sub-
jected only to the migratory flights.

Besides tomatoes and sugar beets, many other crops and weeds are sus-
ceptible. The harboring of both the beet leafhopper and the curly-top
virus on certain weeds in areas of the southern San Joaquin Valley pro-
vides an additional hazard to tomato growing in those localities.

Symptoms (fig. 39) of tomato curly top are inward rolling of the leaf-
lets along the midrib; downward curving of the petioles and midrib,

The Production of Tomatoes in California

giving the leaf a drooping but not wilted appearance ; thickening, crisp-
ing, and yellowing of the leaves ; complete cessation of growth resulting
in the stunting of the plant; erect, rigid habit of growth; and purple
discoloration of the leaf veins and on the stems. Most of the infection
occurs during the early growth of the plant, and such plants bear little
or no fruit and what fruits are produced ripen very small.

Fig. 39. — Symptoms of tomato curly top. Note the inward rolling of the indi-
vidual leaflets, the downward curving of the petiole and midrib, the erect habit
of growth, and the stunted condition. On infected plants the leaves become
crisp, yellow, and thickened; and a purple discoloration is evident on the leaf
veins and stems. (From Ext. Cir. 66.)

There is relatively infrequent spread from tomato to tomato, most of
the danger occurring when leafhoppers first come into tomato fields
from infected beets or other host plants. Infection of tomatoes often
follows the harvest of near-by beet fields. To date there is no adequate
means of preventing or controlling tomato curly top.

Tomato Mosaic. — This disease is more prevalent and widespread than
either of the other two common virus diseases, spotted wilt and curly top.

58 California Agricultural Extension Service [Cir. 104

Though it has no definite geographic limitations within the state, it is
much less destructive to the crop.

Mosaic is characterized by a mottling and puckering of the leaflets and
by a slight reduction in size of the plant and its yield. Some of the strains
of the virus produce a rather brilliant mottling of the leaves correspond-
ing to what is known as yellow or aucuba mosaic. This type frequently
produces in the pigment of the fruit a faint calico pattern, which usually,
but not always, tends to disappear at maturity.

Unlike spotted wilt and curly top, mosaic is also easily spread by
contact in any operation involving handling of the plants, such as trans-
planting. The mosaic virus endures prolonged drying and, being preva-
lent in the tobacco crop, is present in much commercial smoking and
chewing tobacco, and this is an important original source of infection for
tomatoes. Workers who have handled cigarette, cigar, pipe, or chewing
tobacco may readily infect seedlings during transplanting to the plant
bed and then further spread infection when the transplants are pulled
and set in the field. A few mosaic plants in the plant beds are a dangerous
source of infection when the plants are set in the field. Washing the
hands thoroughly with ordinary laundry soap will remove the virus and
is recommended for transplanters.

Fernleaf Mosaic. — Frequently a few scattered plants show the shoe-
string or fernleaf type of mosaic, and heavy outbreaks of this disease
have occurred in the Brentwood area. In this disease the plant is greatly
dwarfed and the leaflets are narrowed so that often not much more than
the midribs are left (fig. 40). Infected plants bear few or no salable
fruits. The fruits are usually dwarfed and misshapen (fig. 41). The dis-
ease is caused by the virus of cucumber mosaic. It is transmitted by
aphids usually in the plant beds prior to setting in the field. Spraying
the plant beds with nicotine or rotenone is recommended if aphids are
present. Weeds and cucurbits near plant beds may be sources of infec-
tion and should be destroyed.

Blossom-End Rot. — Blossom-end rot often occurs in the early set of
fruit and is apparently caused by high temperatures and deficient soil
moisture, and is therefore noninfectious. Under such a condition, con-
ceivably, water may be withdrawn from the fruits with the result that
the surface tissues at the blossom end are killed and a large, flattened,
brown, dead area is formed (fig. 42). Rot-producing fungi entering
through the killed tissue often aggravate the trouble. In some fields it
has seemed likely that blossom-end rot resulted from postponing the
first irrigation too long.

Yellowing and Sunscald. — When the fruit is exposed to the sun by
premature death of the older leaves, two types of injury may occur.

The Production of Tomatoes in California

Fig. 40. — Fernleaf , or shoestring, mosaic caused by the cucumber-
mosaic virus spread by aphids in the plant bed.

Usually the stem end of the fruit remains yellow and does not turn red
(fig. 43). Often, however, the sun injury is more severe and causes on
the exposed side of the fruit a large, light-colored, dead area (sunscald)
which is often invaded by molds and rot-producing fungi.

Growth Cracks and Catface. — Growth cracks about the stem end
are important mainly because rot-producing organisms invade the fruit
through these wounds. Catface is an enlarged ugly scar at the blossom
end, often accompanied by extreme lop-sidedness of the fruit.

California Agricultural Extension Service

[Cir. 104

Alkali and Boron Injury. — In certain areas in some fields, marginal
browning of the leaf margins (fig. 44) tending to extend inward between
the veins may occur rather generally over the plant. This usually indi-
cates excess alkali or boron in the soil.

Fig. 41. — Effect of fernleaf mosaic on the fruits.

Fig. 42. — Symptoms of blossom-end rot on tomato fruits. (From Bui. 239.)

Psyllid Yellows. — This disease is induced by the feeding of the tomato
psyllid, Paratrioza cocker elli (a jumping plant louse), apparently as a
result of some toxic substance injected by the insects. Psyllid yellows has
been serious on potatoes in a few districts in California and more exten-
sively in some of the Rocky Mountain states, but only recently has it been

The Production op Tomatoes in California

;-.. < ^X

Fig. 43. — Yellow-end (or green-end) caused by exposure to sun. The
stem end fails to color properly when the fruit ripens.

'mm

' 1

Fig. 44. — Marginal and interveinal browning of the leaflets caused
probably by excess alkali or boron in the soil.

62 California Agricultural Extension Service [ Cir - 104

recognized as a factor in tomato production in California. It occurs
under cool conditions mainly along the coast and in the early crop near
the Salton Sea. It is not a virus disease.

The symptoms of this disease in some ways closely resemble those of
curly top. (The latter, however, induces more intense yellowing and
stiffness of the leaves and more rapid death. ) Psyllid yellows produces
a puckering of the very young leaflets followed by dwarfing, upward
folding along the midrib, and curling and twisting of the petiole. These
changes may be accompanied by a conspicuous purpling of the margins
and veins of the leaflets. Complete destruction of the tomato plant rarely
occurs unless large numbers of insects infest very young plants. Normal
growth is resumed if the insects are removed or destroyed.

THE TOMATO DISEASE-CONTROL PROGRAM

Aside from market fluctuations, tomato diseases present an important
hazard to profitable production. Fortunately certain precautions pre-
vent losses. These precautions are given below, together with the page
in this circular where detailed directions may be found :

1. Use seed free of bacterial canker, obtained from canker-free fields,
or that which has been properly fermented (p. 49-51).

2. For control of bacterial canker, disinfect the seed with bichloride of
mercury solution (p. 51 ) . After drying, dust the seed with yellow copper
oxide for damping-off control (p. 42).

3. Use disease- and nematode-f ree soil in the plant beds and especially
avoid soil in which tomatoes have recently been grown. Old lumber used
in building plant-bed frames should be disinfected with copper sulfate
(p. 51).

4. Water and ventilate plant beds carefully to minimize loss from
damping-off and to produce stocky, vigorous plants (p. 42).

5. Spray seedlings with yellow copper oxide to control damping-off
(p. 42). '

6. Practice sanitation near plant beds — that is, destroy weeds, cucur-
bits, and ornamentals that harbor virus diseases (p. 56, 58).

7. Avoid use of tobacco when handling plants, or wash hands with soap
and water to remove mosaic virus (p. 58) .

8. Do not top plants (p. 50) .

9. Do not use transplants from beds infected with nematodes or bac-
terial canker (p. 41, 51).

10. Do not use transplants showing black stem cankers of early blight.
Rogue out stunted or sick plants before transplanting (p. 48) .

11. Practice crop rotation to avoid diseases produced by soil-infesting
organisms (p. 41, 42, 43) .

The Production of Tomatoes in California 63

12. Whenever possible use varieties resistant to fusarium wilt and to
verticillium wilt (p. 43).

13. Prevent loss from late blight by using bordeaux mixture (p. 45).

ACKNOWLEDGMENTS

The authors acknowledge with thanks the assistance of the following
individuals in preparing this circular : Messrs. E. L. Abernathy, B. T.
Booye, F. A. Dixon, M. W. Gardner, Charles Jandt, J. B. Kendrick,
G. C. Hanna, P. A. Minges, P. G. Smith, W. H. Nixon, G. W. Scott, R. V.
Sharer, and F. L. Winter. Additional acknowledgment of assistance is
given in the main body of the circular. Farm advisors have also been
of material assistance.

25w-6,'42(9955)